Maternal and perinatal outcomes following pre-Delta, Delta, and Omicron SARS-CoV-2 variants infection among unvaccinated pregnant women in France and Switzerland: a prospective cohort study using the COVI-PREG registry
Authors: Guillaume Favre, Emeline Maisonneuve, Léo Pomar, Charlotte Daire, Christophe Poncelet, Thibaud Quibel, Cécile Monod, Begoña Martinez de Tejada, Leonhard Schäffer, Andrea Papadia, Anda Petronela Radan, Monya Todesco-Bernasconi, Yves Ville, Cora Alexandra Voekt, Béatrice Eggel-Hort, Romina Capoccia-Brugger, Silke Johann, Claudia Grawe, Sophie Defert, Nicolas Mottet, Christian R. Kahlert, Charles Garabedian, Loïc Sentilhes, Brigitte Weber, Steffi Leu, Dirk Bassler, Karine Lepigeon, Ursula Winterfeld, Alice Panchaud, David Baud, Irene Hoesli, Sonia Campelo, Véronique Othenin-Girard, Anett Hernadi, Maria Luisa Gasparri, Antonilli Morena, Christian Polli, Edoardo Taddei, Karoline Aebi-Popp, Luigi Raio, Daniel Surbek, Mirjam Moser, Laurent Salomon, Johana Sichitiu, Julien Stirnemann, Jérôme Dimet, Tina Fischer, Louise Ghesquiere, Amaury Brot, Clémence Houssin, Aurélien Mattuizzi, Stefanie Sturm, Caroline Eggemann, Edouard Ha, Jérôme Mathis, Marie-Claude Rossier, Andrea Bloch, Martin Kaufmann, Carina Britschgi, Panagiotis Kanellos, Bénédicte Breton, Carolin Blume, Stylianos Kalimeris, Arnaud Toussaint, Guillaume Ducarme, Chloé Moreau, Hélène Pelerin, Mohamed Derouich, Cecile Le Parco, Gaetan Plantefeve, Anis Feki, Gaston Grant, Kathrin Bütikofer, Ina Hoffmann, Jessica Maisel, Elke Barbara Prentl, Brigitte Frey Tirri, Grit Vetter, Lucie Sedille, Michel Boulvain, Annina Haessig
Journal: The Lancet Regional Health - Europe (2023)

SARS-CoV-2 positive pregnant women are at higher risk of adverse outcomes, but little evidence is available on how variants impact that risk. We aim to evaluate maternal and perinatal outcomes among unvaccinated pregnant women that tested positive for SARS-CoV-2, stratified by pre-Delta, Delta, and Omicron periods.This prospective study enrolled women from March 2020 to September 2022. Exposure to the different SARS-CoV-2 variants was defined by their periods of predominance. The primary outcome was severe maternal adverse outcome defined as either intensive care unit admission, acute respiratory distress syndrome, advanced oxygen supplementation, or maternal death. The secondary outcomes were preterm birth and other perinatal outcomes.Overall, 1402, 262, and 391 SARS-CoV-2 positive pregnant women were enrolled during the pre-Delta, Delta, and Omicron periods respectively. Severe maternal adverse outcome was reported in 3.4% (n = 947/1402; 95% confidence intervals (95%CI) 2.5-4.5), 6.5% (n = 7/262; 95%CI 3.8-10.2), and 1.0% (n = 4/391; 95%CI 0.3-2.6) of women during the pre-Delta, Delta, and Omicron periods. The risk of severe maternal adverse outcome was higher during the Delta vs pre-Delta period (adjusted risk ratio (aRR) = 1.8; 95%CI 1.1-3.2) and lower during the Omicron vs pre-Delta period (aRR = 0.3; 95%CI, 0.1-0.8). The risks of hospitalization for COVID-19 were 12.6% (n = 176/1402; 95%CI 10.9-14.4), 17.2% (n = 45/262; 95%CI 12.8-22.3), and 12.5% (n = 49/391; 95%CI 9.4-16.2), during the pre-Delta, Delta, and Omicron period, respectively. Pregnancy complications occurred after SARS-CoV-2 exposure in 30.0% (n = 363/1212; 95%CI 27.4-32.6), 35.2% (n = 83/236; 95%CI 29.1-41.6), and 30.3% (n = 105/347; 95%CI 25.5-35.4) of patients during the pre-Delta, Delta, and Omicron periods, respectively. Stillbirths were reported in 0.5% (n = 6/1159; 95%CI 0.2-1.1), 2.8% (n = 6/210; 95%CI 1.0-6.0), and 0.9% (n = 2/213; 95%CI 0.1-3.4) or patients during the pre-Delta, Delta, and Omicron periods respectively.The Delta period was associated with a higher risk of severe maternal adverse outcome and the Omicron period with a lower risk of severe adverse outcome compared to pre-Delta era. The reported risk of hospitalization was high during the Omicron period and should not be trivialized.Swiss Federal Office of Public Health, Fondation CHUV.